About J0621+1002
J0621+1002 is a rare pulsar. It spins once every 28.854 ms, has a dispersion measure of 36.55 pc cm⁻³ and carries a surface magnetic field around 1.18×10^9 G.
The collapsed core of a star that exploded: about one and a half Suns of matter crushed into a ball the size of a city, held up only by the refusal of neutrons to be squeezed further.